Interference level variation mitigation for satellite communicaton systems

ABSTRACT

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for adjusting the transmission power of satellite transceivers based on estimated interference. In some implementations, a satellite transceiver receives a data structure that specifies an interference compensation value for at least one frequency channel on which the satellite transceiver can transmit. The interference compensation value for the frequency channel is based on estimated interference imposed on satellite transmissions transmitted by the transceiver on the frequency channel. The transceiver receives data specifying a second transmit frequency channel to use for a second satellite transmission. A first interference compensation value for a first frequency channel and a second interference compensation value for the second frequency channel are identified from the data structure. The power level of the transmitter of the transceiver is adjusted based on a difference between the second interference compensation value and the first interference compensation value.

BACKGROUND

In a Demand Assigned Multiple Access (DAMA) satellite communicationsystem, communication channels are temporarily assigned to gateways andterminals. However, the amount of interference may vary based on theassigned channel. For example, one channel may be subject to moreinterference than another channel. This can result in a differentsignal-to-noise ratio (SNR) each time a terminal or gateway is assignedto a different channel.

SUMMARY

In some implementations, a satellite transceiver (e.g., a satelliteterminal or gateway) can adjust its transmit power based on a channel towhich the transceiver is assigned. A channel can include one or morecarrier frequencies or frequency ranges, e.g., a frequency range fortransmitting data and/or a frequency range for receiving data. In a DAMAsatellite communication system, the transceiver may be assigneddifferent transmit frequency channels for different satellitetransmissions.

The satellite transceiver can determine an appropriate transmit powerusing a data structure, e.g., a table, that specifies interferencecompensation values for frequency channels on which the transceiver isconfigured to transmit. The interference compensation value for atransmit frequency channel can be based on estimated interferenceimposed on the transceiver's satellite transmissions using that transmitfrequency channel, e.g., as determined from power, directivity, and/orother characteristics of other satellite transceivers and/or thesatellite with which the transceiver is communicating. The interferencecompensation values can be predetermined and stored at the transceiver,allowing the transceiver to compensate for a switch between any channelin a set to any other channel in the set without requiring activeanalysis of current channel conditions. When the frequency channel onwhich the transceiver transmits is changed from a first transmitfrequency channel to a second transmit frequency channel, thetransceiver can adjust its transmit power based on a difference betweenthe interference compensation value for the first transmit frequencychannel and the interference compensation value for the second transmitfrequency channel.

The level of interference that affects satellite transmissions may varybased on the transmit frequency channel used for the transmissions. Forexample, some transmit frequency channels may be used for higher symbolrate transmissions than others, which may result in more interference atthose transmit frequencies. In a particular example, different portionsof the frequency spectrum may be assigned as channels operating atdifferent symbol rates. This can result in different symbol ratecarriers interfering with each other in different portions of thefrequency spectrum and therefore different combined interference at thedifferent portions of the frequency spectrum, as well as different SNRrequirements for using the channels operating at different symbol rates.In addition, some transmit frequency channels may have more interferers(e.g., more terminals and gateways that transmit on the frequencychannels) than other frequency channels.

The techniques described below allow a satellite transceiver to adjustits power based on the estimated interference level so that thetransceiver can maintain the same (or similar) signal quality across thevarious frequency channels. This results in higher quality signals,reduced packet error rates, and less interference imposed on othersignals due to transmitting data at higher transmit power levels thanrequired for a transmit frequency channel.

By estimating the level of interference for each transmit frequencychannel based on power, directivity, and/or other characteristics ofother satellite transceivers and/or the satellite with which thetransceiver is communicating, the amount of computing resources used toestimate the levels of interference can be reduced. In someimplementations, a transceiver can perform a ranging operation using afirst frequency channel to determine a transmit power level for thefirst frequency channel. This ranging operation usually involvestransmitting data using the first frequency channel, receiving signalquality data for each transmission, and adjusting the transmit poweruntil the signal quality meets a signal quality target. Thereafter, theranging operation is not needed for transmissions on other channels.Using a table of interference compensation values to adjust the transmitpower for other frequencies avoids the need to range the transceiverusing the other frequency channels. This reduces the amount of bandwidthconsumed in determining transmit power levels for transceivers andreduces the amount of computing resources and satellite communicationresources used in determining the power levels. By limiting the amountof transmissions used for ranging, e.g., to a single channel at thebeginning of a communication session, the interference typically causedby frequent ranging is significantly reduced. In addition, by settingthe transmit power levels appropriately, the system avoids transmittingwith excessive power, which wastes energy and causes unnecessaryinterference for other transceivers, while also avoiding transmittingwith insufficient power, which could result in high error rates or dataloss.

By using a table of interference compensation values to determineadjustments to transmit power levels, the table can be stored at thetransceiver without consuming a significant amount of memory. The tablealso allows the transceiver to adjust its transmit power level inresponse to a transmit frequency change quickly using minimal computingresources. The table can be updated quickly, e.g., by a gateway, if thesatellite system layout has changed, e.g., a new gateway or terminal isadded to the satellite system.

In one general aspect, the techniques disclosed herein describe methodsof adjusting transmission power. According to some of the methods, asatellite transceiver receives a data structure that specifies aninterference compensation value for at least one transmit frequencychannel of a set of frequency channels on which the satellitetransceiver is configured to transmit. The interference compensationvalue for the at least one transmit frequency channel is based onestimated interference imposed on satellite transmissions transmitted bythe satellite transceiver on the at least one transmit frequencychannel. The satellite transceiver receives data specifying a secondtransmit frequency channel associated with a second satellitetransmission. In response to receiving the data specifying the secondtransmit frequency channel, a transmit frequency channel of atransmitter of the satellite transceiver is adjusted from a firsttransmit frequency channel to the second transmit frequency channel. Afirst interference compensation value for the first transmit frequencychannel and a second interference compensation value for the secondtransmit frequency channel are identified from the received datastructure. A transmit power level of the transmitter of the satellitetransceiver is adjusted based on a difference between the secondinterference compensation value and the first interference compensationvalue. The satellite transceiver transmits data at the adjusted transmitpower level and on the second transmit frequency channel.

In some implementations, adjusting the transmit power of the transmitterof the satellite transceiver includes determining, as the adjustedtransmit power, a sum of (i) a first transmit power level used by thetransmitter of the satellite transceiver for a first data transmissionusing the first transmit frequency channel and (ii) the differencebetween the second interference compensation value and the firstinterference compensation value.

In some implementations, the interference compensation value for the atleast one transmit frequency channel is based on an estimated total pathsignal-to-noise ratio for the at least one transmit frequency channel.The total path includes a first signal from the satellite transceiver toa satellite on the at least one transmit frequency channel and a secondsignal from the satellite to a second satellite transceiver differentfrom the satellite transceiver.

In some implementations, the satellite transceiver includes a satelliteterminal and the second satellite transceiver includes a satellitegateway. In these implementation, the first signal can include a returnuplink signal and the second signal can include a return downlinksignal.

In some implementations, the satellite transceiver includes a satellitegateway and the second satellite transceiver includes a satelliteterminal. In these implementations, the first signal can include aforward uplink signal and the second signal comprises a forward downlinksignal.

In some implementations, the interference compensation value for the atleast one transmit frequency channel is based on a difference between(i) an estimated total path signal-to-noise ratio for any one frequencychannel of the set of frequency channels and (ii) the estimated totalpath signal-to-noise ratio for the at least one transmit frequencychannel.

In some implementations, the estimated total path signal-to-noise ratiofor the at least one transmit frequency channel is based on estimatedinterference imposed on signals transmitted by the satellite transceiveron the at least one transmit frequency channel by one or more satellitegateways that transmit on the at least one transmit frequency channeland one or more satellite terminals that transmit on the at least onetransmit frequency channel.

In some implementations, the estimated interference imposed on signalstransmitted by the satellite transceiver on the at least one transmitfrequency channel by one or more satellite gateways and one or moresatellite terminals is based on, for each satellite gateway, adirectional power of the satellite gateway and directivity of an antennaof the satellite at a location of the satellite gateway. The estimatedinterference imposed on signals transmitted by the satellite transceivercan be also be based on, for each different satellite terminal, adirectional power of the satellite terminal and directivity of anantenna of the satellite at a location of the satellite terminal.

In some implementations, the estimated interference imposed on signalstransmitted by the satellite transceiver on the at least one transmitfrequency channel by one or more a satellite gateways and one or moredifferent satellite terminals is based on, for each satellite gateway,performance data for an antenna of the satellite gateway and directivityof an antenna of the satellite. The estimated interference imposed onsignals transmitted by the satellite transceiver can also be based on,for each different satellite terminal, performance data for an antennaof the different satellite terminal and directivity of an antenna of thesatellite.

Some implementations include receiving updated interference compensationvalues and using the updated interference compensation values to adjustthe transmit power of the transmitter of the satellite transceiver. Theupdated interference compensation values can be based on a change to asatellite system that includes the satellite transceiver. The change tothe satellite system can include an addition or removal of at least oneof (i) a satellite terminal, (ii) a satellite gateway, or (iii) aportion of the channels of which signals are being transmitted byterminals or gateways of the satellite system.

In one general aspect, the techniques disclosed herein describe methodsof generating data structures that include interference compensationvalues. According to some of the methods, one or more computers receivean antenna profile for a satellite. The antenna profile represents apower level of satellite signals at multiple locations. The one or morecomputers receive, for each of one or more satellite terminals, datarepresenting transmit power of the satellite terminal at each frequencychannel of a set of frequency channels on which a particular satellitetransceiver is configured to transmit. The one or more computersreceive, or each of one or more satellite gateways, data representingtransmit power of the satellite gateway at each frequency channel of theset of frequency channels. The one or more computers determine, for atleast one frequency channel of the set of frequency channels, anestimated signal-to-noise ratio for the particular satellite transceiverwhen the particular satellite transceiver transmits at the frequencychannel based on the antenna profile for the satellite, the datareceived for each satellite terminal and the data received for eachsatellite gateway. The one or more computers generate a data structurethat specifies, for the at least one frequency channel of the set offrequency channels, an interference compensation value for the at leastone frequency channel. The interference compensation value for the atleast one frequency channel is based on a difference between thesignal-to-noise ratio for a particular frequency channel of the set offrequency channels and the signal-to-noise ratio for the at least onefrequency channel. The data structure is provided to the particularsatellite transceiver.

In some implementations, the particular frequency channel is thefrequency channel of the set of frequency channels having the greatestsignal-to-noise ratio of the set of frequency channels.

In some implementations, the estimated signal-to-noise ratio for theparticular satellite transceiver when the particular satellitetransceiver transmits at each particular frequency channel is furtherbased on a location of each of the one or more satellite terminals and alocation of each of the one or more satellite gateways.

In some implementations, the estimated signal-to-noise ratio for theparticular satellite transceiver when the particular satellitetransceiver transmits at each particular frequency channel is furtherbased on performance data for a respective antenna of each of the one ormore satellite terminals and performance data for a respective antennaof each of the one or more satellite gateways.

In some implementations, the signal-to-noise ratio for the particularfrequency channel is the signal-to-noise ratio for a frequency channelhaving the highest signal-to-noise ratio of the set of frequencychannels. In some implementations, the particular satellite transceiveris one of a satellite terminal or a satellite gateway.

Other embodiments include corresponding systems, apparatus, and softwareprograms, configured to perform the actions of the methods, encoded oncomputer storage devices. For example, some embodiments include asatellite terminal and/or a satellite gateway configured to perform theactions of the methods. A device or system of devices can be soconfigured by virtue of software, firmware, hardware, or a combinationof them installed so that in operation cause the system to perform theactions. One or more software programs can be so configured by virtue ofhaving instructions that, when executed by data processing apparatus,cause the apparatus to perform the actions.

The details of one or more embodiments of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages of thesubject matter will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram that illustrates an example of a system in which asatellite terminal adjusts its transmit power level based on transmitfrequency channel.

FIG. 2 is a diagram that illustrates example interferers that imposeinterference on a return uplink signal transmitted by a satelliteterminal.

FIG. 3 is a diagram that illustrates example interferers that imposeinterference on a return downlink signal transmitted by a satellite to agateway.

FIG. 4 is a diagram that illustrates an example of a system thatdetermines interference compensation values for terminals and generatestables that include the values.

FIG. 5 is a flow diagram that illustrates an example process forgenerating a data structure that include interference compensationvalues for a particular satellite terminal.

FIG. 6 is a flow diagram that illustrates an example process foradjusting transmit power of a satellite terminal and transmitting dataat the adjusted transmit power.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 1 is a diagram that illustrates an example of a system 100 in whicha satellite terminal 110 adjusts its transmit power level based ontransmit frequency channel. The system 100 includes a satellite 140 of asatellite network that can include multiple satellites, and a gateway150. The terminal 110 can communicate with the gateway 150 bytransmitting data in a return uplink signal 111 to the satellite 140.The satellite 140 can transmit the data to the gateway 150 in a returndownlink signal 151. The gateway 150 can also send data to the terminal110 by transmitting the data in a forward uplink signal to the satellite140. The satellite 140 can transmit the data to the terminal 110 in aforward downlink signal to the terminal 110.

The system 100 can also include one or more additional terminals 130 andone or more additional gateways 160 that transmit and/or receive signalsthat impose interference on the return uplink signal 111 and/or thereturn downlink signal 151, as described in more detail below withreference to FIGS. 2 and 3. For example, the terminals 130 and gateways160 may transmit and/or receive signals using one or more transmitcommunication channels that are also used by the terminal 110.

The gateway 150 includes a satellite transceiver 152 and a channelassigner 154. The transceiver 152 can transmit signals to the satellite140 and receive signals from the satellite 140. The channel assigner 154can assign transmit frequency channels to terminals, such as theterminal 110 and/or the terminals 130. For example, the gateway 150 mayuse DAMA technology to assign transmit frequency channels to theterminals. Similarly, the terminal 110 can be configured to transmitdata at multiple transmit frequency channels.

The channel assigner 154 can receive a request for a channel assignmentfrom the terminal 110 and assign a transmit frequency channel to theterminal 110 in response to the request. For example, the terminal 110can submit a request to the gateway 150 for each data transmission bythe terminal 110. The transceiver 152 can transmit the assigned transmitfrequency channel to the terminal 110 via the satellite 140. In turn,the terminal 110 can transmit data in a return uplink signal 111 usingthe assigned transmit frequency channel.

The terminal 110 includes a tuner 112, a power controller 114, aninterference compensation data table 116, a transmitter 118, and anantenna 120. The tuner 112 can adjust the transmit frequency channelused by the terminal 110 to transmit data. For example, as describedabove, the terminal 110 can be configured to transmit data usingmultiple transmit frequency channels. The tuner 112 can switch theterminal between the multiple transmit frequency channels, e.g., basedon an assigned transmit frequency channel received from the gateway 150.

The power controller 114 can set a transmit power level of thetransmitter 118 for a particular data transmission. The power controller114 can set the transmit power level based on the assigned transmitfrequency channel for the data transmission. As described above, thelevel of interference may vary based on transmit frequency channel. Toensure high signal quality, e.g. greater than a threshold SNR, the powercontroller 114 can adjust the transmit power level based on an expectedlevel of interference for the transmit frequency channel.

In some implementations, the power controller 114 adjusts the transmitpower level based on interference compensation values stored in theinterference compensation table 116. Although in this example theinterference compensation values are stored in a table, the interferencecompensation values can be stored in other data structures, e.g.,databases, registers, etc. The interference compensation table 116includes an interference compensation value for each of one or moretransmit frequency channels on which the terminal 110 transmits data.For example, the terminal 110 is configured to transmit on “Z” transmitfrequency channels, where “Z” is an integer greater than two but couldbe an integer greater than one in other examples. The interferencecompensation values can be pre-calculated by one or more computers,e.g., by the interference compensation table generator 410 of FIG. 4,and provided to the terminal 110.

The interference compensation value for a transmit frequency channel canbe based on estimated interference imposed on satellite transmissionstransmitted by the terminal 110 on the transmit frequency channel. Insome implementations, the interference compensation value for a transmitfrequency channel is based on an estimated interference imposed on thetotal path from the terminal 110 to the gateway 150 for the transmitfrequency channel. The estimated interference along the total path for atransmit frequency channel can be based on a combination of theestimated interference imposed on the return uplink signal 111 and theestimated interference imposed on the downlink signal 151, as describedin more detail below.

In some implementations, the interference compensation value for atransmit frequency channel is based on the estimated total path SNR ofthe communication path from the terminal 110 to the gateway 150 for thetransmit frequency channel. The estimated total path SNR for thetransmit frequency channel can be based on a combination of theestimated SNR of the return uplink signal 111 and the estimated SNR ofthe return downlink signal 151. The estimated total path SNR for eachtransmit frequency channel can be expressed in decibels.

In some implementations, the interference compensation values arenormalizations of the estimated total path interference or the estimatedtotal path SNRs that are based on the estimated total path interferenceto make power adjustments for channel changes quicker and lesscomputationally intensive. For example, the estimated total path SNRscan be normalized using the estimated total path SNR for one of thetransmit frequency channels. In a particular example, the interferencecompensation value for each particular transmit frequency channel isbased on a difference between the highest estimated total path SNR ofthe transmit frequency channels and the total path SNR for theparticular transmit frequency channel. In this way, the interferencecompensation value for the transmit frequency channel having the highestestimated total path SNR would be zero and the interference compensationvalue for each other transmit frequency channel that has a lowerestimated total path SNR would be some number greater than zero. Thisresults in each interference compensation value for the transmitfrequency channels having a lower estimated total path SNR having apositive value that can be used to increase the transmit power level forthese transmit frequency channels. Example techniques for determininginterference compensation values are described in more detail below.

When the tuner 112 changes the transmit frequency from one transmitfrequency channel to another transmit frequency channel (e.g. from afirst transmit frequency channel to a second transmit frequencychannel), the power controller 114 can adjust the transmit power of thetransmitter 118 using the interference compensation values stored in theinterference compensation table 116. The adjusted power level is basedon a first power level used for a first transmission on the firsttransmit frequency channel, the interference compensation value for thefirst transmit frequency channel, and the interference compensationvalue for the second transmit frequency channel. In someimplementations, the adjusted power level is based on the first powerlevel used for the first transmission on the first transmit frequencychannel and a difference between the interference compensation value forthe first transmit frequency channel and the interference compensationvalue for the second transmit frequency channel.

The first and second transmissions can be in any sequence. For example,the second transmission on the second transmit frequency channel canoccur after the first transmission on the first transmit frequencychannel. The second transmission may be immediately after the firsttransmission (e.g., no intervening transmissions by the transceiver) orthere may be one or more intervening transmissions between the firsttransmission and the second transmission. For example, the transceivercan transmit a first transmission on the first transmit frequencychannel. Later, the transceiver can transmit a second transmission onthe second transmit frequency channel. Between the first and secondtransmissions, the transceiver may use zero or more other transmitfrequency channels to transmit data. Thus, the first transmission may bereferred to as a previous transmission on a previous transmit frequencychannel and the second transmission may be referred to as a nexttransmission on a next transmit frequency channel.

For example, the interference compensation value for channel 1 is 1.0decibels (dB) and the interference compensation value for channel 2 is0.0 dB. In this example, consider that channel 2 had the highest totalpath SNR resulting in the interference compensation value of 0.0 dB andthat the total path SNR for channel 1 was lower (e.g., 1.0 dB lower)than the total path SNR for channel 2. Thus, in this example, channel 1receives more interference than channel 2. If the tuner 112 changes thetransmit frequency channel from channel 1 to channel 2, the powercontroller 114 can determine the transmit power level for thetransmission on channel 2 using equation 117. In equation 117, thetransmit power level for the transmission on channel 2 is a sum of thetransmit power level for the previous transmission of channel 1 and thedifference between the interference compensation value for channel 2(0.0 dB) and the interference compensation value for channel 1 (1.0 dB).As the difference is a negative number (−1.0), this may result in adecrease in transmit power for channel 2 relative to channel 1 aschannel 2 has a higher SNR than channel 1 and therefore needs lesstransmit power to have a sufficient SNR. For example, the adjustedtransmit power level may be 1.0 dB less than the transmit power levelfor the previous transmission.

The power controller 114 can determine a transmit power level each timethe tuner 112 changes the transmit frequency channel and provide dataspecifying the power level to the transmitter 118 so that thetransmitter 118 transmits data at the appropriate power level for thetransmit frequency channel. In some implementations, the powercontroller 114 can also adjust the power level based on other factors,such as weather, cross-talk from other channels, etc. For example, thepower controller 114 can adjust the transmit power based on transmitfrequency channel using the interference compensation values and adjustthe transmit power based on weather and/or other factors.

The transmitter 118 can transmit data using the antenna 120 based on thetransmit power level determined by the power controller 114 and on thetransmit frequency channel set by the tuner 112. Although not shown, theterminal 110 can also include a receiver that receives data from thegateway 150. For example, the terminal 110 can include a satellitetransceiver that includes the transmitter 118 and a receiver.

In some implementations, the terminal 110 can perform a ranging processto determine an appropriate power level for a particular transmitfrequency channel. During the ranging process, the terminal 110 cantransmit data to the gateway 150 and receive signal quality indicatorsbased on the transmissions. The terminal 110 can adjust the power levelfor the particular transmit frequency channel until the signal qualityindicators indicate that the signal quality is within a threshold amountof a target signal quality. Rather than performing the ranging processfor each transmit frequency channel, the terminal 110 can use theinterference compensation values to adjust the power level of thetransmitter 118 for other transmit frequency channels. For example, somesatellite systems would perform ranging for every channel which usesmuch more power, bandwidth, and causes interference. Using theinterference compensation values as described herein allows for rangingto be performed for one channel, reducing consumption of power,bandwidth and interference.

In some implementations, when a terminal 110 is placed into service orinitialized, the terminal 110 can be turned on and the terminal 110 canperform the ranging process for one of its transmit frequency channels.As described above, the terminal 110 can transmit data to the gateway150, receive signal quality indicators based on the transmissions, andadjust the power level for the transmit frequency channel until thesignal quality indicators indicate that the signal quality is within athreshold amount of a target signal quality to perform the rangingprocess. The terminals 110 can also receive, e.g., from the gateway 150,a data structure that includes interference compensation values for theterminal 110.

When the terminal 110 is ready to transmit data, the terminal 110 canrequest a channel assignment from the gateway 150. The terminal 110 canreceive the channel assignment from the gateway 150 and determine atransmit power level for the assigned channel based on the power leveldetermined for the one frequency channel during the ranging process andinterference compensation values for the one frequency channel and theassigned channel. For example, the terminal 110 can adjust the powerlevel from the power level of the one frequency channel to anappropriate power level for the assigned channel based on a differencebetween the interference compensation value for the assigned channel andthe interference compensation value for the one channel. The terminalcan then transmit data on the assigned channel at the adjusted powerlevel.

Although not shown, the gateway 150 can include an interferencecompensation table and a power controller similar to the interferencecompensation table 116 and the power controller 114, respectively. Thetransceiver 152 can adjust the power of forward uplink signalstransmitted from the gateway 150 to the satellite based on interferencecompensation values determined for each transmit frequency channel ofthe gateway 150. The interference compensation value for each transmitfrequency channel of the gateway 150 can be determined based onestimated amounts of interference imposed on forward uplink signalstransmitted from the gateway 150 to the satellite 140 using the transmitfrequency channel and forward downlink signals transmitted from thesatellite to the terminal 110 using the transmit frequency channel.

Similar to the interference compensation values for the terminal 110,the interference compensation value for a transmit frequency channel ofthe gateway can be based on a normalization of the estimated total pathSNR of the communication path from the gateway 150 to the terminal 110for the transmit frequency channel. The estimated total path SNR for thetransmit frequency channel can be based on a combination of theestimated SNR of the forward uplink signal and the estimated SNR of theforward downlink signal, e.g., expressed in decibels. The normalizationcan be based on the SNR for one of the transmit frequency channels ofthe gateway 150, e.g., the highest SNR, similar to that of theinterference compensation value normalization for the terminal 110.

The gateway 150 can also perform a ranging process to determine anappropriate transmit power level for one of the transmit frequencychannels and then use the transmit power level for the one transmitfrequency channel and the interference compensation values for thefrequency channels to adjust the transmit power level for each transmitfrequency channel. For example, when the gateway 150 adjusts itstransmit frequency channel from a first frequency channel to a secondfrequency channel, the gateway 1150 can determine an adjusted powerlevel for the second frequency channel based on a first power level usedfor the first transmission on the first frequency channel and adifference between the interference compensation value for the firstfrequency channel and the interference compensation value for the secondfrequency channel, as described above for the terminal 110.

The gateway 150 can store an interference compensation table for eachterminal with which the gateway 150 communicates. For example, thegateway 150 may communicate with terminals in different locations thatare affected differently by interference and therefore have differentinterference compensation values for the different frequency channels ofthe gateway 150. Similarly, if a terminal communicates with multiplegateways, the terminal can store an interference compensation table foreach gateway and use the interference compensation table for the gatewaywith which the terminal is communicating.

FIG. 2 is a diagram that illustrates example interferers that imposeinterference on the return uplink signal 111 transmitted by thesatellite terminal 110. The interferers include other satelliteterminals 230 a and 230 b and other satellite gateways 260 a and 260 b.Although two terminals 230 a and 230 b and two gateways 260 a and 260 bare illustrated in FIG. 2, other numbers of terminals and gateways mayimpose interference on signals communicated between the terminal 110 andthe gateway 150.

Data transmissions by the terminals 230 a and 230 b can imposeinterference on return uplink signals transmitted by the terminal 110.For example, the terminal 110 may transmit data to the satellite 140 ona first spot beam from a first location. The terminal 230 a may transmitdata to the satellite 140 (or another satellite) on a second spot beam231 a from a second location and the terminal 230 b may transmit data tothe satellite 140 (or another satellite) on a third spot beam 231 b froma third location. If each terminal transmits on the same frequencychannel at the same time, the terminals may impose interference on eachother's transmitted signals.

The amount of interference imposed on a terminal's transmitted signalfor each transmit frequency channel may depend on the relative locationof the terminals, the transmit power of the terminals, the directionalpower of the terminals, the performance of the terminals' antennas, thebandwidth of the transmitted signals, the roll-off and polarization ofthe transmitted signals, and/or the directivity pattern of the satellite140. For example, two terminals that are close together may impose moreinterference on each other than two terminals that are further apart.Example techniques for determining the amount of interference imposed byeach interfering terminal and for each transmit frequency channel aredescribed in detail below.

The terminals that impose interference on data transmissions of theterminal 110 can vary based on the transmit frequency channel of theterminal 110. For example, a first set of terminals may each beconfigured to transmit on a first transmit frequency channel on whichthe terminal 110 transmits. A second set of terminals may each beconfigured to transmit on a second transmit frequency channel on whichthe terminal 110 transmits. One or more terminals in the first set maynot be members of the second set. Similarly, one or more terminals inthe second set may not be members of the first set. Thus, datatransmissions on the first transmit frequency channel may have differentinterferers than data transmissions on the second transmit frequencychannel.

Similarly, data transmissions by the gateways 260 a and 260 b can alsoimpose interference on return uplink signals transmitted by the terminal110. For example, the terminal 110 may transmit data to the satellite140 on a first spot beam from a first location. The gateway 260 a maytransmit data to the satellite 140 (or another satellite) on a secondspot beam 261 a from a second location and the terminal 260 b maytransmit data to the satellite 140 (or another satellite) on a thirdspot beam 261 b from a third location. If each gateway transmits on thesame frequency channel as the terminal 100 at the same time, thegateways may impose interference on the terminal's transmitted signals.

The amount of interference imposed on a terminal's transmitted signalfor each transmit frequency channel may depend on the relative locationof the gateways 261 a and 261 b and the terminal 110, the transmit powerof the gateways 260 a and 260 b, the directional power of the gateways260 a and 260 b, the performance of the gateways' antennas the bandwidthof the transmitted signals, the roll-off and polarization of thetransmitted signals, and/or the directivity pattern of the satellite140. Example techniques for determining the amount of interferenceimposed by each interfering gateway and for each transmit frequencychannel are described in detail below.

Similar to the terminals, the gateways that impose interference on datatransmissions of the terminal 110 can vary based on the transmitfrequency channel of the terminal 110. For example, data transmissionson a first transmit frequency channel may have different gatewaysinterferers than data transmissions on a second transmit frequencychannel. Similarly, the terminals 230 a and 230 b and the gateways 261 aand 261 b can impose interference on forward uplink signals transmittedby the gateway 150 to the satellite 140.

FIG. 3 is a diagram that illustrates example interferers that imposeinterference on the return downlink signal 151 transmitted by thesatellite 140 to the gateway 150. The interferers include signalstransmitted from the satellite 140 to other satellite terminals 330 aand 330 b and other satellite gateways 360 a and 360 b. Although twoterminals 330 a and 330 b and two gateways 360 a and 360 b areillustrated in FIG. 3, signals transmitted from the satellite 140 toother numbers of terminals and gateways may impose interference onsignals communicated between the satellite 140 and the gateway 150.

Data transmissions from the satellite 140 to the terminals 330 a and 330b can impose interference on return downlink signals transmitted by thesatellite 140 to the gateway 150. For example, the satellite 140 maytransmit data on a first spot beam to the gateway 150 located at a firstlocation. The satellite 140 may transmit data on a second spot beam 331a to the terminal 330 a located at a second location and the satellite140 may transmit data on a third spot beam 331 b to the terminal 330 blocated at a third location. If the satellite 140 transmits the data toeach terminal on the same frequency channel at the same time, theterminals may impose interference on each other's received signals.

The amount of interference imposed on return downlink signal 151 foreach frequency channel may depend on the relative location of theterminals, the bandwidth of the transmitted signals, the directionalpower of the terminals, the performance of the terminals' antennas, theroll-off and polarization of the transmitted signals, and/or thedirectivity pattern of the satellite 140. Example techniques fordetermining the amount of interference imposed by each interferingterminal and for each transmit frequency channel are described in detailbelow.

The terminals for which satellite transmissions impose interference onreturn downlink signal 151 vary based on the frequency channel of thedownlink signal 151. For example, a first set of terminals may each beconfigured to receive on a first frequency channel on which thesatellite 140 transmits the return downlink signals 151. A second set ofterminals may each be configured to receive on a second frequencychannel on which the satellite 140 transmits the return downlink signals151. One or more terminals in the first set may not be members of thesecond set. Similarly, one or more terminals in the second set may notbe members of the first set. Thus, return downlink signals 151 on thefirst frequency channel may have different interferers than returndownlink signals 151 on the second frequency channel.

Similarly, data transmissions from the satellite 140 to the gateways 360a and 360 b can also impose interference on return downlink signals 151transmitted by the satellite 140. For example, the satellite 140 maytransmit data on a first spot beam to the gateway 150 located at a firstlocation. The satellite 140 may transmit data on a second spot beam 361a to the gateway 360 a located at a second location and the satellite140 may transmit data on a third spot beam 361 b to the gateway 360 blocated at a third location. If the satellite 140 transmits the data toeach gateway on the same frequency channel at the same time, theterminals may impose interference on each other's received signals.

The amount of interference imposed on return downlink signal 151 foreach frequency channel may depend on the relative location of thegateways, the bandwidth of the transmitted signals, the directionalpower of the gateways, the performance of the gateways' antennas theroll-off and polarization of the transmitted signals, and/or thedirectivity pattern of the satellite 140. Example techniques fordetermining the amount of interference imposed by each interferinggateway and for each frequency channel of the return downlink signal 151are described in detail below.

Similar to the terminals, the gateways for which satellite transmissionsimpose interference on return downlink signals 151 can vary based on thetransmit frequency channel of the satellite 140. For example, datatransmissions on a first transmit frequency channel may have differentgateways interferers than data transmissions on a second transmitfrequency channel.

FIG. 4 is a diagram that illustrates an example of a system 400 thatdetermines interference compensation values for terminals and generatestables that include the values. The system 400 includes an interferencecompensation table generator 410 that generates interferencecompensation tables for the terminals based on data received fromsatellite manufacturers and/or operators 422, terminal manufacturersand/or operators 424 and/or gateway manufacturers and/or operators 426.

The interference compensation table generator 410 can include one ormore computers that include a data collector 412, an interferencecompensation value generator 414, and a table generator 416. The datacollector 412 can aggregate data received from the satellitemanufacturers/operators 422, terminal manufacturers/operators 424 and/orgateway manufacturers/operators 426.

The data collector 412 can receive, e.g., from data published orprovided by a satellite manufacturer/operator 422, data about asatellite that communicates with terminals 450-A-450-Z for whichinterference compensation tables are generated. In some implementations,a user of the interference compensation table generator 410 may providethe data to the data collector 412. The data can include data specifyinguplink and downlink frequency channels used by the satellite, one ormore antenna profiles for the satellite, and/or noise performance of thesatellite's receiver. An antenna profile can include, for each frequencychannel of the satellite's uplink and downlink, an antenna pattern forthe satellite's antenna at that frequency channel. The antenna patternfor a particular frequency channel can include a directivity patternthat indicates the power of satellite signals at locations within anarea of interest for the satellite.

The data collector 412 can receive, e.g., from data published orprovided by a terminal manufacturer/operator 424, data about a satelliteterminal manufactured or operated by the terminal manufacturer/operator424. In some implementations, a user of the interference compensationtable generator 410 may provide the data to the data collector 412. Thedata about a satellite terminal can include the geographic location ofthe terminal, the frequency channels on which the terminal transmitsand/or receives data, data specifying the directional power of theterminal when the terminal is transmitting data, and/or performance datafor the terminal's antenna. In some implementations, the directionalpower of the terminal may be expressed as the Equivalent IsotropicallyRadiated Power (EIRP) of the terminal. In some implementations, theperformance data for the terminal's antenna is expressed as thegain-to-noise-temperature (G/T) of the antenna.

The data collector 412 can receive, e.g., from data published orprovided by a gateway manufacturer/operator 426, data about a satellitegateway manufactured or operated by the gateway manufacturer/operator426. In some implementations, a user of the interference compensationtable generator 410 may provide the data to the data collector 412. Thedata about a satellite gateway can include the geographic location ofthe gateway, the frequency channels on which the gateway transmitsand/or receives data, data specifying the directional power of thegateway when the gateway is transmitting data, and/or performance datafor the gateway's antenna. In some implementations, the directionalpower of the gateway may be expressed as the EIRP of the gateway. Insome implementations, the performance data for the gateway's antenna isexpressed as the G/T of the antenna.

The data collector 412 can also receive data about the currentconfiguration of the satellite system. The configuration of thesatellite system may identify the gateways and terminals in the system,their locations, which of the satellite's uplink and downlink frequencychannels that are being used, the frequency channels being used by eachterminal and gateway in the system, the symbol rate, roll-off andplacement of carriers in those frequency channels, and/or other dataabout the satellite system.

The interference compensation value generator 414 can use the datacollected by the data collector 414 to generate interferencecompensation values for each terminal 450-A-450-B. The interferencecompensation values for each particular terminal can include aninterference compensation value for each channel on which the terminaltransmits data.

To determine the interference compensation values for a particularterminal, e.g., terminal A 450-A, the interference compensation valuegenerator 414 can identify the transmit frequency channels on which theterminal 450-A transmits data, e.g., based on data received from themanufacturer or operator of the terminal 450-A. For each transmitfrequency channel, the interference compensation value generator 414 canidentify the return uplink interferers and the return downlinkinterferers for that transmit frequency channel.

The return uplink interferers for a transmit frequency channel caninclude other terminals and gateways that can transmit data on thetransmit frequency channel, as shown in FIG. 2. The return downlinkinterferers for a transmit frequency channel can include satellitetransmissions to other terminals and gateways that can receive data onthe transmit frequency channel, as shown in FIG. 3. The interferencecompensation value generator 414 can identify the interferers for theterminal 450-A based on the data specifying the frequency channels onwhich the terminals and gateways transmit and/or receive data receivedfrom the terminal manufacturers/operators 424 and the gatewaymanufacturers/operators 426. For example, the interference compensationvalue generator 414 can evaluate the data to identify each terminal andgateway that includes, as one of its channels, the transmit frequencychannel of interest.

In some implementations, the interference compensation value generator414 can also use the data about the current configuration of thesatellite system to identify the interferers. For example, although aterminal may transmit data on the transmit frequency channel, theterminal may be configured to not use that channel in the currentconfiguration of the satellite system. In this example, the terminal maynot be identified as an interferer.

The interference compensation value generator 414 can then identify, foreach interferer, an estimated amount of interference imposed on thereturn uplink signal transmitted by the terminal 450-A to the satelliteand/or an estimated amount of interference imposed on the returndownlink signal transmitted by the satellite to the gateway by theinterferer using the data collected by the data collector 412.

For the return uplink signal transmitted by the terminal 450-A, theamount of interference imposed by each interfering terminal orinterfering gateway can be based on the directional power of thetransmitter of the interfering terminal or interfering gateway (e.g.,the EIRP of the terminal or gateway), the directivity of the satellitereceive antenna at the location of the interfering terminal orinterfering gateway, the gain (e.g., G/T) of the satallite's receiveantenna, path loss between the satellite and Earth, and/or crosspolisolation if a cross-pol transmitter or receiver is used. For example,higher EIRPs and higher directivity at the location of the interferingterminal or interfering gateway can result in a higher estimated amountof interference than lower EIRPs and/or lower directivity. In addition,the estimated amount of interference of each interfering terminal orinterfering gateway can be based on the distance between the terminal450-A and the interfering terminal or interfering gateway, e.g., greaterdistance resulting in less interference.

The estimated amount of interference for each uplink interferer (e.g.,interfering terminal or gateway) can be based on, e.g., equal to, anestimated power level of signals transmitted by the uplink interferer atthe satellite 140 on the frequency channel of interest. For eachtransmit frequency channel, the interference compensation valuegenerator 414 can estimate, for each uplink interferer, a power level ofsignals transmitted by the uplink interferer on the frequency channel atthe satellite's receiver using the directional power of the uplinkinterferer (e.g., the EIRP of the interferer), the directivity of thesatellite receive antenna at the location of the uplink interferer, thegain (e.g., G/T) of the satellite's receive antenna, path loss betweenthe satellite and Earth, crosspol isolation if a cross-pol transmitteror receiver is used, and/or the relative locations of the terminal 450-Aand the uplink interferer.

In some implementations, the estimated amount of interference for anuplink interferer on a particular frequency channel is based on acombination of the EIRP of the interferer's transmitter, the path lossbetween the satellite and Earth, the G/T of the satellite's receiveantenna, and crosspol isolation (if a cross-pol transmitter or receivedis used). For example, the estimated amount of interference for anuplink interferer may be equal to a sum of the EIRP and the G/T minusthe path loss and the crosspol isolation.

As the estimated amount of interference is determined for each transmitfrequency channel of the terminal 450-A, the estimated amount ofinterference imposed on the return uplink signal transmitted by theterminal 450-A on a particular transmit frequency channel by aparticular interferer can be based on the directivity of the satellitereceive antenna at the particular transmit frequency channel at thelocation of the interferer.

The total estimated amount of interference imposed on the return uplinksignal for a particular transmit frequency channel can be based on acombination of the estimated amount of interference imposed by eachinterfering terminal and each interfering gateway. The total estimatedamount of interference imposed on the return uplink signal for aparticular transmit frequency channel can also be based on noiseperformance of the satellite receiver. The total interference imposed onthe return uplink signal for each transmit frequency channel (f_(k)) ofa terminal can be used to determine an estimated SNR for the transmitfrequency (f_(k)) using Equation 1 below:

$\begin{matrix}{{\frac{C_{up}}{N_{up} + I_{up}}\left( f_{k} \right)} = \frac{C_{up}\left( f_{k} \right)}{{N_{up}\left( f_{k} \right)} + {\Sigma_{i = 1}^{N}{I_{{gw},{up}}\left( {i,f_{k}} \right)}} + {\Sigma_{j = 1}^{M}{I_{{term},{up}}\left( {j,f_{k}} \right)}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In Equation 1,

$\frac{C_{up}}{N_{up} + I_{up}}\left( f_{k} \right)$

is the uplink SNR for frequency (f_(k)); C_(up)(f_(k)) is the carrierpower per unit bandwidth at frequency (f_(k)); N_(up)(f_(k)) is thenoise power per unit bandwidth at the satellite receiver at frequency(f_(k)); f_(k)) is the interfering gateway power per unit bandwidth fromgateway (i) at the satellite at frequency (f_(k)) and I_(term,up)(j,f_(k)) is the interfering terminal power per unit bandwidth fromterminal (j) at the satellite at frequency (f_(k)). In this equation,there are “N” gateways that transmit on frequency channel (f_(k)) and“M” terminals that transmit on frequency channel (f_(k)). Thus, the SNRfor frequency (f_(k)) is based on a ratio between (i) the carrier powerper unit bandwidth at frequency (f_(k)) and (ii) a combination of thenoise power per unit bandwidth at the satellite at frequency (f_(k)), asum of the gateway interfering power per unit bandwidth of theinterfering gateways at frequency (f_(k)) and a sum of the terminalinterfering power per unit bandwidth of the interfering terminals atfrequency (f_(k)).

For the return downlink signal transmitted by the satellite to thegateway in response to the return uplink signal transmitted by theterminal 450-A to the satellite, the estimated amount of interferenceimposed by each interfering terminal or interfering gateway can be basedon the performance data for the receive antenna of the interferingterminal or interfering gateway, e.g., the G/T of the antenna, and thedirectivity of the satellite transmit antenna at the location of theinterfering terminal or interfering gateway. In addition, the estimatedamount of interference of each interfering terminal or interferinggateway can be based on the distance between the terminal 450-A and theinterfering terminal or interfering gateway, e.g., greater distanceresulting in less interference.

The estimated amount of interference for each downlink interferer (e.g.,satellite transmissions to an interfering terminal or gateway) can bebased on, e.g., equal to, an estimated power level of signalstransmitted by the satellite to the downlink interferer at the gatewayfor which interference compensation values are being determined on thefrequency channel of interest. For each transmit frequency channel, theinterference compensation value generator 414 can estimate, for eachdownlink interferer, a power level of signals transmitted by thesatellite on the frequency channel at the gateway's receiver using theperformance data for the receive antenna of the interfering terminal orinterfering gateway, e.g., the G/T of the antenna, the directivity ofthe satellite transmit antenna at the location of the interferingterminal or interfering gateway, the EIRP of the satellite'stransmitter, the distance between the gateway and the interferingterminal or interfering gateway and/or crosspol isolation if a cross-poltransmitter or receiver is used.

In some implementations, the estimated amount of interference for adownlink interferer on a particular frequency channel is based on acombination of the EIRP of the satellite's transmitter, the path lossbetween the satellite and Earth, the G/T of the gateway's receiveantenna, and crosspol isolation (if a cross-pol transmitter or receivedis used). For example, the estimated amount of interference for downlinkinterferer may be equal to a sum of the EIRP and the G/T minus the pathloss and the crosspol isolation.

As the estimated amount of interference is determined for each transmitfrequency channel of the terminal 450-A, the estimated amount ofinterference imposed on the return downlink signal on a particulartransmit frequency channel by a particular interferer can be based onthe directivity of the satellite transmit antenna at the particulartransmit frequency channel at the location of the interferer.

The total estimated amount of interference imposed on the returndownlink signal for a particular transmit frequency channel can be basedon a combination of the estimated amount of interference imposed bysatellite transmissions to each interfering terminal and eachinterfering gateway. The total estimated amount of interference imposedon the return downlink signal for a particular transmit frequencychannel can also be based on noise performance of the gateway receiverfor the gateway that receives data from the terminal (e.g., gateway150). The total interference imposed on the return downlink signal foreach transmit frequency channel (f_(k)) of a terminal can be used todetermine an estimated SNR for the transmit frequency (f_(k)) usingEquation 2 below:

$\begin{matrix}{{\frac{C_{dwn}}{N_{dwn} + I_{dwn}}\left( f_{k} \right)} = \frac{C_{dwn}\left( f_{k} \right)}{{N_{dwn}\left( f_{k} \right)} + {\Sigma_{i = 1}^{N}{I_{{gw},{dwn}}\left( {i,f_{k}} \right)}} + {\Sigma_{j = 1}^{M}{I_{{term},{dwn}}\left( {j,f_{k}} \right)}}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

In Equation 2,

$\frac{C_{dwn}}{N_{dwn} + I_{dwn}}\left( f_{k} \right)$

is the downlink SNR for frequency (f_(k)); C_(dwn)(f_(k)) is the carrierpower per unit bandwidth at frequency (f_(k)); N_(dwn)(f_(k)) is thenoise power per unit bandwidth at the gateway receiver at frequency(f_(k)) I_(gw,dwn)(i, f_(k)) is the portion of satellite power togateway (i) per unit bandwidth at the receiver of victim gateway (e.g.,gateway 150) at frequency (f_(k)) and I_(term,dwn)(j, f_(k)) is theportion of satellite power to terminal (j) per unit bandwidth at thereceiver of the victim gateway at frequency (f_(k)). In this equation,there are “N” other gateways that receive satellite signals on frequencychannel (f_(k)) and “M” terminals that receive satellite signals onfrequency channel (f_(k)). Thus, the SNR for frequency (f_(k)) is basedon a ratio between (i) the carrier power per unit bandwidth at frequency(f_(k)) and (ii) a combination of the noise power per unit bandwidth atthe gateway at frequency (f_(k)), a sum of the interfering power perunit bandwidth meant for other gateways at frequency (f_(k)) and a sumof the interfering power per unit bandwidth meant for terminals atfrequency (f_(k)).

The interference compensation value generator 414 can determine anestimated total path SNR for each transmit frequency channel of eachterminal 450-A-450-Z based on a combination of the estimated SNRs forthe transmit frequency channel of the terminal determined usingEquations 1 and 2. Combining Equations 1 and 2, Equation 3 below can beused to determine the estimated total path SNR for a transmit frequencychannel of a satellite terminal:

$\begin{matrix}{{\frac{C}{N + 1}\left( f_{k} \right)} = \frac{1}{\left( {\frac{1}{\frac{C_{dwn}}{\left( {N_{dwn} + I_{dwn}} \right.}\left( f_{k} \right)} + \frac{1}{\frac{C_{up}}{\left( {N_{up} + I_{up}} \right)}\left( f_{k} \right)}} \right)}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

In Equation 3,

$\frac{C}{N + 1}\left( f_{k} \right)$

is the estimated total path SNR for frequency channel (f_(k)); C_(dwn)is the carrier power per unit bandwidth at frequency (f_(k)); N_(dwn) isthe noise power per unit bandwidth at the gateway receiver at frequency(f_(k)); I_(dwn) is the total estimated downlink interference imposed bythe satellite terminals at frequency (f_(k)); N_(up) is the noise powerper unit bandwidth at the satellite receiver at frequency (f_(k)); andI_(up) is the total estimated uplink interference imposed by theinterfering gateways and the interfering terminals at frequency (f_(k));

For each terminal 450-A-450-Z, the interference compensation valuegenerator 414 can determine the estimated total path SNR at eachtransmit channel frequency of the terminal using Equations 1-3 above andthe data collected by the data collector 412. The interferencecompensation value generator 414 can use the estimated total path SNRsfor the terminal to determine the interference compensation values forthe terminal.

In some implementations, the interference compensation value generator414 normalizes the estimated total path SNRs to determine theinterference compensation values. The interference compensation valuegenerator 414 can normalize the estimated total path SNRs for theterminal using the estimated total path SNRs for a particular beam onwhich the terminal will be transmitting or all beams of the satellitesystem. For example, the interference compensation value generator 414can determine estimated total path SNRs for only the transmit frequencychannels on which the terminal is configured to transmit or for alltransmit frequency channels available to the satellite system of whichthe terminal is a part.

The interference compensation value generator 414 can normalize theestimated total path SNRs using one of the estimated total path SNRs.For example, the interference compensation value generator 414 cannormalize the estimated total path SNRs using the highest estimatedtotal path SNR or the lowest estimated total path SNR. For example,consider a terminal that communicates on three transmit frequencychannels A, B, and C. The estimated total path SNR for channel A may be37 dB; the estimated total path SNR for channel B may be 41 dB; and theestimated total path SNR for channel C may be 28 dB. In this example,the estimated total path SNR for channel B may be used to normalize thethree estimated total path SNRs as channel B has the highest estimatedtotal path SNR. To normalize the estimated total path SNRs, theinterference compensation value generator 414 can determine thedifference between the estimated total path SNR for channel B and theestimated path for the channel. In this example, the normalizedinterference compensation value for channel A may be 4 dB (41-37).Similarly, the normalized interference compensation value for channel Bmay be 0 dB (41-41) and the normalized interference compensation valuefor channel C may be 13 dB (41-28).

The interference compensation value generator 414 can generate theinterference compensation values for each terminal 450-A-450-Z andprovide the values to the table generator 416. The table generator 416can generate, for each terminal, an interference compensation table thatincludes the interference compensation values for the terminal. Thetable generator 416 can provide each interference compensation table toits corresponding terminal. For example, the table generator 416 canprovide the interference compensation tables to a gateway that transmitsthe interference compensation tables to their corresponding terminals.

The interference compensation table generator 410 can update the tables,e.g., in response to a change to the satellite system. For example, if anew gateway or terminal is added to the system, this may add a newinterferer for at least some of the frequency channels. In anotherexample, the satellite or a terminal or gateway may be configured totransmit or receive on a frequency channel on which it previously didnot transmit, adding a new interfere to that frequency channel. Theinterference compensation value generator 414 can determined updatedinterference compensation values and the table generator 416 cangenerate updated interference compensation tables based on the updatedvalues. The table generator 416 can provide the updated interferencecompensation tables to the terminals 450-A-450-D, e.g., via the gateway.

The interference compensation table generator 410 can determineinterference compensation values and generate interference compensationtables for gateways in a similar manner and using the same or similardata. For example, the interference compensation value generator 414 canuse equation 3 above to determine an estimated total path SNR for eachtransmit frequency channel of the gateway and normalize the values togenerate the interference compensation values for the gateway.

The total path SNR for each frequency channel can be based on acombination of the estimated power level at the satellite's receiver ofeach forward uplink interferer on the frequency channel and theestimated power level at the terminal of each forward downlinkinterferer on the frequency channel. The estimated power level at thesatellite's receiver for a forward uplink interferer can be based ondirectional power of the uplink interferer (e.g., the EIRP of theinterferer), the directivity of the satellite receive antenna at thelocation of the uplink interferer, and the relative locations of thegateway and the uplink interferer. The estimated power level at theterminal's receiver for a forward downlink interferer can be based onthe performance data for the receive antenna of the interfering terminalor interfering gateway, e.g., the G/T of the antenna, the directivity ofthe satellite transmit antenna at the location of the interferingterminal or interfering gateway, and/or the distance between the gatewayand the interfering terminal or interfering gateway.

FIG. 5 is a flow diagram that illustrates an example process 500 forgenerating a data structure that includes interference compensationvalues for a particular satellite terminal. The process may be performedby a system that includes one or more computers. The one or morecomputers can include one or more processors. The one or more computerscan also include one or more data storage devices storing instructionsthat, when executed, cause the one or more computers to perform theactions of the process 500. The steps of the process 500 may beperformed in the order shown in FIG. 5, or in another order. A similarprocess can be used to generate a data structure that includesinterference compensation values for a particular satellite gateway.

In step (502), an antenna profile for a satellite is received. Theantenna profile can include data representing a power level of satellitesignals transmitted by the satellite at multiple locations. The antennaprofile can also include data representing a power of satellite signalsreceived by the satellite from multiple locations. The antenna profilemay be received from a manufacturer or an operator of the satellite.

In step (504), data for each of one or more satellite terminals isreceived. The one or more satellite terminals may be satellite terminalsthat are part of the same satellite communication system as theparticular satellite terminal and/or that communicate on the sametransmit frequency channels as the particular satellite terminal.

The data for each terminal can represent transmit power of the satelliteterminal at each frequency channel of a set of frequency channels onwhich a particular satellite terminal is configured to transmit. Thedata for each satellite terminal can also include the geographiclocation of the terminal, the frequency channels on which the terminaltransmits and/or receives data, data specifying the directional power ofthe terminal when the terminal is transmitting data, and/or performancedata for the terminal's antenna. In some implementations, thedirectional power of the terminal may be expressed as the EIRP of theterminal. In some implementations, the performance data for theterminal's antenna is expressed as the G/T of the antenna.

In step (506), data for each of one or more satellite gateways isreceived. The one or more satellite terminals may be satellite gatewaysthat are part of the same satellite communication system as theparticular satellite terminal and/or that communicate on the sametransmit frequency channels as the particular satellite terminal.

The data for each gateway can represent the transmit power of thesatellite gateway at each frequency channel of the set of frequencychannels. The data for each gateway can also include the geographiclocation of the gateway, the frequency channels on which the gatewaytransmits and/or receives data, data specifying the directional power ofthe gateway when the gateway is transmitting data, and/or performancedata for the gateway's antenna. In some implementations, the directionalpower of the gateway may be expressed as the EIRP of the gateway. Insome implementations, the performance data for the gateway's antenna isexpresses as G/T of the antenna.

In step (508), for at least one frequency channel for the set offrequency channels, an estimated SNR is determined for the particularsatellite terminal when the satellite terminal transmits on the at leastone the frequency channel. For example, the estimated SNR for aparticular frequency channel can be an estimated total path SNR that isbased on estimated interference imposed on the particular satelliteterminal's transmissions on the particular frequency channel. Theestimated SNR for a frequency channel can be based on the antennaprofile for the satellite, the data received for each satelliteterminal, and the data received for each satellite gateway, as describedabove.

In step (510), a data structure is generated. The data structure, whichmay be a table, can specify, for the at least one frequency channel ofthe set of frequency channels, an interference compensation value forthe at least one frequency channel. The interference compensation valuefor a particular frequency channel can be based on a difference betweenthe SNR for a particular frequency channel of the set of frequencychannels and the signal-to-noise ratio for the particular frequencychannel. For example, the interference compensation value for aparticular frequency channel can be based on a difference between thehighest SNR of the set of frequency channels and the SNR for theparticular frequency channel.

In step (512), the data structure is provided to the particularsatellite terminal. For example, a gateway with which the particularsatellite terminal communicates may send the data structure to theparticular satellite terminal. The satellite terminal can use theinterference compensation values stored in the data structure to adjustits transmit power level based on the transmit frequency channel towhich the particular satellite terminal is assigned.

FIG. 6 is a flow diagram that illustrates an example process 600 foradjusting transmit power of a satellite terminal and transmitting dataat the adjusted transmit power. The process 600 may be performed by asatellite terminal, such as the satellite terminal 110 of FIG. 1. Thesatellite terminal may include one or more processors. The satelliteterminal may also include one or more data storage devices storinginstructions that, when executed, cause the satellite terminal toperform the actions of the process 600. The steps of the process 600 maybe performed in the order shown in FIG. 6, or in another order. Asimilar process can be used to adjust the transmit power of a satellitegateway.

In step (602), the satellite terminal receives a data structure thatspecifies an interference compensation value for at least one frequencychannel of a set of frequency channels at which the satellite terminalis configured to transmit. For example, the terminal may be part of aDAMA system in which the terminal transmits on an assigned transmitfrequency channel for each data transmission and the assigned transmitfrequency channel may be different for different data transmissions. Thedata structure can include an interference compensation table thatstores the interference compensation values. The satellite terminal canstore the data structure in memory of the satellite terminal, e.g., in ahard drive, flash drive, or other type of data storage device.

As described above, the interference compensation value for the at leastone transmit frequency channel can be based on estimated interferenceimposed on satellite transmissions transmitted by the satellite terminalon the particular transmit frequency channel. In some implementations,the interference compensation value for a transmit frequency channel canbe based on a total path SNR for the transmit frequency channel. Forexample, the interference compensation value for a particular transmitfrequency channel can be based on (e.g., equal to or proportional to) adifference between a total path SNR for a transmit frequency channelhaving the highest SNR of the transmit frequency channels and the totalpath SNR for the particular transmit frequency channel. The interferencecompensation value for each transmit frequency channel can be expressedin decibels as the SNRs may also be expressed in decibels.

At step (604), the satellite terminal receives data specifying a secondtransmit frequency channel for a second satellite transmission. Forexample, the satellite terminal may have transmitted data on a firsttransmit frequency channel. After some time, the satellite terminal canreceive a request to transmit additional data. The satellite terminalcan request, e.g., from a satellite gateway, a transmit frequencychannel to use for transmitting the additional data. The satellitegateway can provide, to the satellite terminal, data specifying thesecond transmit frequency channel on which the satellite terminal cantransmit the additional data. In this example, the first transmitfrequency channel may be referred to as a previous transmit frequencychannel for a previous transmission and the second transmit frequencychannel may be referred to as a next transmit frequency channel for anext transmission. The second transmit frequency channel may be usedimmediately after the first transmit frequency channel, e.g., with nointervening transmit frequency channels or there may be one or moreintervening transmit frequency channels used between the first andsecond transmit frequency channels.

At step (606), the satellite terminal adjusts a transmit frequencychannel of a transmitter of the satellite terminal from the firsttransmit frequency channel to the second transmit frequency. Thesatellite terminal can include a tuner that adjusts the transmitfrequency channel of the transmitter from the first transmit frequencychannel to the second transmit frequency channel specified by the datareceived from the satellite gateway.

At step (608), the satellite terminal identifies, from the received datastructure, a first interference compensation value for the firsttransmit frequency channel and a second interference compensation valuefor the second transmit frequency channel. For example, the satelliteterminal can access an interference compensation table and identify theinterference compensation values for the first transmit frequencychannel and the second transmit frequency channel.

At step (610), the satellite terminal adjusts a transmit power level ofthe transmitter based on a difference between the second interferencecompensation value and the first interference compensation value. Insome implementations, the adjusted power level is based on a firsttransmit power level used to transmit on the first transmit frequencychannel and a difference between the first interference compensationvalue and the second interference compensation value. For example, theadjusted power level is based on (e.g., equal to or proportional to) asum of the first transmit power level used to transmit on the firsttransmit frequency channel and the difference between the secondinterference compensation value and the first interference compensationvalue. The adjusted power level can be based on an increase or decreasein transmit power that would provide similar signal quality on thesecond transmit frequency channel as was provided on the first transmitfrequency channel in view of the difference in estimated interferencefor the two transmit frequency channels.

At step (612), the satellite terminal transmits data at the adjustedtransmit power level. For example, the transmitter can use an antenna totransmit the data on the second transmit frequency channel and at theadjusted power level. The satellite terminal can transmit the data to asatellite on a return uplink signal that is on the second transmitfrequency channel. The satellite can receive the data and transmit thedata to the satellite gateway.

Embodiments of the invention and all of the functional operationsdescribed in this specification may be implemented in digital electroniccircuitry, or in computer software, firmware, or hardware, including thestructures disclosed in this specification and their structuralequivalents, or in combinations of one or more of them. Embodiments ofthe invention may be implemented, in part, as one or more computerprogram products, i.e., one or more modules of computer programinstructions encoded on a computer-readable medium for execution by, orto control the operation of, data processing apparatus. The computerreadable medium may be a non-transitory computer readable storagemedium, a machine-readable storage device, a machine-readable storagesubstrate, a memory device, a composition of matter effecting amachine-readable propagated signal, or a combination of one or more ofthem. The term “data processing apparatus” encompasses all apparatuses,devices, and machines for processing data, including by way of example aprogrammable processor, a computer, or multiple processors or computers.The apparatus may include, in addition to hardware, code that creates anexecution environment for the computer program in question, e.g., codethat constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them.

A computer program (also known as a program, software, softwareapplication, script, or code) may be written in any form of programminglanguage, including compiled or interpreted languages, and it may bedeployed in any form, including as a stand-alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program may be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programmay be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this specification may beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows may also be performedby, and apparatus may also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

While this specification contains many specifics, these should not beconstrued as limitations on the scope of the invention or of what may beclaimed, but rather as descriptions of features specific to particularembodiments of the invention. Certain features that are described inthis specification in the context of separate embodiments may also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment mayalso be implemented in multiple embodiments separately or in anysuitable subcombination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination may in some casesbe excised from the combination, and the claimed combination may bedirected to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments, and it should beunderstood that the described program components and systems maygenerally be integrated together in a single software product orpackaged into multiple software products.

Thus, particular embodiments of the invention have been described. Otherembodiments are within the scope of the following claims. For example,the actions recited in the claims may be performed in a different orderand still achieve desirable results.

What is claimed is:
 1. A method comprising: receiving, by a satellitetransceiver, a data structure that specifies an interferencecompensation value for at least one transmit frequency channel of a setof frequency channels on which the satellite transceiver is configuredto transmit, wherein the interference compensation value for the atleast one transmit frequency channel is based on estimated interferenceimposed on satellite transmissions transmitted by the satellitetransceiver on the at least one transmit frequency channel; receiving,by the satellite transceiver, data specifying a second transmitfrequency channel associated with a second satellite transmission; inresponse to receiving the data specifying the second transmit frequencychannel: adjusting a transmit frequency channel of a transmitter of thesatellite transceiver from a first transmit frequency channel to thesecond transmit frequency channel; identifying, from the received datastructure, a first interference compensation value for the firsttransmit frequency channel and a second interference compensation valuefor the second transmit frequency channel; and adjusting a transmitpower level of the transmitter of the satellite transceiver based on adifference between the second interference compensation value and thefirst interference compensation value; and transmitting, by thesatellite transceiver, data at the adjusted transmit power level and onthe second transmit frequency channel.
 2. The method of claim 1, whereinadjusting the transmit power of the transmitter of the satellitetransceiver comprises determining, as the adjusted transmit power, a sumof (i) a first transmit power level used by the transmitter of thesatellite transceiver for a first data transmission using the firsttransmit frequency channel and (ii) the difference between the secondinterference compensation value and the first interference compensationvalue.
 3. The method of claim 1, wherein the interference compensationvalue for the at least one transmit frequency channel is based on anestimated total path signal-to-noise ratio for the at least one transmitfrequency channel, wherein the total path includes a first signal fromthe satellite transceiver to a satellite on the at least one transmitfrequency channel and a second signal from the satellite to a secondsatellite transceiver different from the satellite transceiver.
 4. Themethod of claim 3, wherein: the satellite transceiver comprises asatellite terminal and the second satellite transceiver comprises asatellite gateway; the first signal comprises a return uplink signal;and the second signal comprises a return downlink signal.
 5. The methodof claim 3, wherein: the satellite transceiver comprises a satellitegateway and the second satellite transceiver comprises a satelliteterminal; the first signal comprises a forward uplink signal; and thesecond signal comprises a forward downlink signal.
 6. The method ofclaim 3, wherein the interference compensation value for the at leastone transmit frequency channel is based on a difference between (i) anestimated total path signal-to-noise ratio for any one frequency channelof the set of frequency channels and (ii) the estimated total pathsignal-to-noise ratio for the at least one transmit frequency channel.7. The method of claim 3, wherein the estimated total pathsignal-to-noise ratio for the at least one transmit frequency channel isbased on estimated interference imposed on signals transmitted by thesatellite transceiver on the at least one transmit frequency channel byone or more satellite gateways that transmit on the at least onetransmit frequency channel and one or more satellite terminals thattransmit on the at least one transmit frequency channel.
 8. The methodof claim 7, wherein the estimated interference imposed on signalstransmitted by the satellite transceiver on the at least one transmitfrequency channel by one or more satellite gateways and one or moresatellite terminals is based on: for each satellite gateway, adirectional power of the satellite gateway and directivity of an antennaof the satellite at a location of the satellite gateway; and for eachdifferent satellite terminal, a directional power of the satelliteterminal and directivity of an antenna of the satellite at a location ofthe satellite terminal.
 9. The method of claim 7, wherein the estimatedinterference imposed on signals transmitted by the satellite transceiveron the at least one frequency channel by one or more a satellitegateways and one or more different satellite terminals is based on: foreach satellite gateway, performance data for an antenna of the satellitegateway and directivity of an antenna of the satellite; and for eachdifferent satellite terminal, performance data for an antenna of thedifferent satellite terminal and directivity of an antenna of thesatellite.
 10. The method of claim 1, further comprising receivingupdated interference compensation values and using the updatedinterference compensation values to adjust the transmit power of thetransmitter of the satellite transceiver, wherein the updatedinterference compensation values are based on a change to a satellitesystem that includes the satellite transceiver.
 11. The method of claim10, wherein the change to the satellite system includes an addition orremoval of at least one of (i) a satellite terminal, (ii) a satellitegateway, or (iii) a portion of the channels of which signals are beingtransmitted by terminals or gateways of the satellite system.
 12. Themethod of claim 1, wherein the data structure specifies a respectiveinterference compensation value for each transmit frequency channel onwhich the satellite transceiver is configured to transmit and the secondsatellite transmission is subsequent to a first satellite transmissionby the satellite transceiver on the first transmit frequency channel.13. A transceiver of a satellite communications system, the transceivercomprising: one or more processors; a transmitter; and one or more datastorage devices storing instructions that, when executed by the one ormore processors, cause the transmitter to perform operations comprising:receiving a data structure that specifies an interference compensationvalue for at least one transmit frequency channel of a set of frequencychannels on which the transmitter is configured to transmit, wherein theinterference compensation value for the at least one transmit frequencychannel is based on estimated interference imposed on satellitetransmissions transmitted by the transmitter on the at least onetransmit frequency channel; receiving data specifying a second transmitfrequency channel associated with a second satellite transmission; inresponse to receiving the data specifying the second transmit frequencychannel: adjusting a transmit frequency channel of the transmitter froma first transmit frequency channel to the second transmit frequencychannel; identifying, from the received data structure, a firstinterference compensation value for the first transmit frequency channeland a second interference compensation value for the second transmitfrequency channel; and adjusting a transmit power level of thetransmitter based on a difference between the second interferencecompensation value and the first interference compensation value; andtransmitting data at the adjusted transmit power level and on the nexttransmit frequency channel.
 14. The transceiver of claim 13, whereinadjusting the transmit power of the transmitter comprises determining,as the adjusted transmit power, a sum of (i) a first transmit powerlevel used by the transmitter for a first data transmission using thefirst transmit frequency channel and (ii) the difference between thesecond interference compensation value and the first interferencecompensation value.
 15. The transceiver of claim 13, wherein theinterference compensation value for the at least one transmit frequencychannel is based on an estimated total path signal-to-noise ratio forthe at least one transmit frequency channel, wherein the total pathincludes a first signal from the transceiver to a satellite on the atleast one transmit frequency channel and a second signal from thesatellite to a second transceiver different from the satellitetransceiver.
 16. A method comprising: receiving, by one or morecomputers, an antenna profile for a satellite, the antenna profilerepresenting a power level of satellite signals at a plurality oflocations; receiving, by the one or more computers and for each of oneor more satellite terminals, data representing transmit power of thesatellite terminal at each frequency channel of a set of frequencychannels on which a particular satellite transceiver is configured totransmit; receiving, by the one or more computers and for each of one ormore satellite gateways, data representing transmit power of thesatellite gateway at each frequency channel of the set of frequencychannels; determining, by the one or more computers and for at least onefrequency channel of the set of frequency channels, an estimatedsignal-to-noise ratio for the particular satellite transceiver when theparticular satellite transceiver transmits at the frequency channelbased on the antenna profile for the satellite, the data received foreach satellite terminal and the data received for each satellitegateway; generating, by the one or more computers, a data structure thatspecifies, for the at least one frequency channel of the set offrequency channels, an interference compensation value for the at leastone frequency channel, wherein the interference compensation value forthe at least one frequency channel is based on a difference between thesignal-to-noise ratio for a particular frequency channel of the set offrequency channels and the signal-to-noise ratio for the at least onefrequency channel; and providing the data structure to the particularsatellite transceiver.
 17. The method of claim 16, wherein theparticular frequency channel is the frequency channel of the set offrequency channels having the greatest signal-to-noise ratio of the setof frequency channels.
 18. The method of claim 16, wherein the estimatedsignal-to-noise ratio for the particular satellite transceiver when theparticular satellite transceiver transmits at each particular frequencychannel is further based on a location of each of the one or moresatellite terminals and a location of each of the one or more satellitegateways.
 19. The method of claim 16, wherein the estimatedsignal-to-noise ratio for the particular satellite transceiver when theparticular satellite transceiver transmits at each particular frequencychannel is further based on performance data for a respective antenna ofeach of the one or more satellite terminals and performance data for arespective antenna of each of the one or more satellite gateways. 20.The method of claim 16, wherein the signal-to-noise ratio for theparticular frequency channel is the signal-to-noise ratio for afrequency channel having the highest signal-to-noise ratio of the set offrequency channels.